Re: would you buy used AGMs?
Seems that AGMs are easier to ruin with bad use practices so I would be very cautious. If I personally knew the past owner and there habits I might. But $100 seems steep for used, given you don't know the history. Is there any warranty. (either original OE or from seller?) Why is the person getting rid of them?
I would look at Sam's Club golf cart batteries. I believe that is what Mainesail recommends and are around $84 to $112 each.